Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia caused by the trinucleotide(CAG) repeat expansion in the alpha1A-voltage-dependent calcium channel gene. In this paper, we describe clinical, neuropathological and genetic characteristics of SCA6. Clinical analysis on 82 affected individuals revealed that SCA6 is characterized by later-onset pure cerebellar syndrome. Phenomenon of anticipation was not obvious, demonstrating another characteristics of SCA6. Neuropathologically, SCA6 brains consistently showed predominant degeneration of the Purkinje cell. In contrast with other CAG repeat diseases, the ubiquitin-positive neuronal intranuclear inclusion was absent in SCA6. Molecular genetically, SCA6 was characterized by an expansion of a small and stable CAG repeat. We conclude that SCA6 has several unique features compared to other CAG repeat diseases.